are two kinds of excommunications. One takes place by a public statement of the proper
authority. The second kind of excommunication is incurred ipso
facto or latae sententiae. That means if you commit a certain crime or sin
(and if all the conditions under law are present), you are by that very fact excommunicated.
An excommunicated person (Canon #133) is
forbidden: 1) to have any ministerial part in the celebration of the sacrifice of the
Eucharist or any other ceremonies of public worship; 2) to celebrate the sacraments
or sacramentals and to receive the sacraments; 3) to exercise any ecclesiastical offices,
ministries or acts of governance.
All excommunications are meant to be medicinal.
They are a kind of shock therapy intended to make sinners aware of the seriousness
of their sin and their spiritual condition and call them to conversion. Because excommunication is a medicinal
penalty, it must be absolved when the person truly repents.